Is it a 390 or a 391 Casting numbers

Hey all you great fordthusiast. I finally know what size my block is, drum-roll................ It's a 360. I did like i read in a post and measured the stroke and it was 3 1/2" on the number one piston. All i did was insert a dowel and had a friend turn the crank one full rotation, as i held a sharpie against the dowel. The mark left was 3 1/2". Now that i know this, i can move on to my performance build. Is there a thread that i can ask advice on my build? Metal on brothers and sisters.